This invention relates to slitting devices and, more particularly, to slitters for slitting continuous sheet material into strips of precise width.
Slitting devices of known type include spaced and parallel rotatable shafts or arbors having cooperating cutting knives thereon. Sheet material, e.g. metal sheet, is fed between the cooperating cutting knives which slit the sheet material into continuous strips of precise width.
In order to adjust the width of the strip or strips being cut, it is desirable to be able to move the slitter knives along the rotatable shafts. For this purpose, hydraulically expandable hubs have been developed, such as those described in Eiting, U.S. Pat. No. 4,541,163, issued Sept. 17, 1985. Such hubs operate on the principle of expanding the diameter of the hub by application of hydraulic pressure to the interior of the hub so as to enable the expanded hub to slide over the surface of the shaft. The hydraulic pressure is applied to an annular chamber defined between a groove in the interior of the hub and the outside diameter of the shaft over which the shaft is to slide. Upon removal of the pressure, the hub returns to the diameter of the shaft and is thereby frictionally secured to the shaft.
To ensure accuracy in the width of the strip being slit, the sheet material must be maintained flat during the actual slitting. This is typically accomplished by employing polyurethane support rings surrounding metal spacers that fit snugly between the slitter knives on a slitting head. A problem that has been encountered is how to easily install these spacers and rings.
This particular problem is accentuated for machines on which the slitter knives are mounted on hydraulically expandable hubs. Thus, when the hydraulically expandable hubs are used, it is a very easy matter to adjust the lateral spacing of the slitter knives themselves. The problem is how to position the fill-in metal spacers and polyurethane rings between the slitter knives with equal ease. Typically, spacers are now used which have been cut in half and which can be reassembled on an arbor and fixed in place with bolts. The polyurethane rings are then slid over the spacers. This is not only time consuming, but such assemblies are prone to mechanical damage when the bolts become cross-threaded and require regular reconditioning.
Another system for varying the support length when the spacing of slitter knives is changed is described in Arima, U.S. Pat. No. 4,757,732, issued July 19, 1988. This system used a series of spacer rollers of different lengths mounted on a rotary support frame. For instance four rollers may be mounted on a rotatable support with separate bearing mountings, etc. This arrangement is both cumbersome and expensive.
It is an object of the present invention to provide a support arrangement for sheet material between the slitter knives that can easily be adjusted when the lateral spacing of the slitter knives is adjusted.